1. Field of the Invention
This invention relates to novel pyranoindolizine derivatives, and more specifically to pyranoindolizine derivatives which are useful as intermediates for the synthesis of camptothecin derivatives having anticancer effects and are represented by the following formula (I): ##STR3## wherein R means a hydrogen atom or hydroxyl group and Q denotes &gt;C.dbd.O or ##STR4## with a proviso that Q is other than &gt;C.dbd.O when R is a hydrogen atom.
2. Description of the Prior Art
Camptothecin derivatives represented by the following formula (II) or (III) have conventionally been known to have excellent anticancer effects [Japanese Patent Laid-Open No. 39683/1983; Tetrahedron 37, 1047(1981)]: ##STR5## It has hence been desired to provide synthetic intermediates suitable for use in the advantageous synthesis of the derivatives.
On the other hand, natural camptothecin represented by the following formula (IV*): ##STR6## has been known to have the S-configuration at the 20 -position thereof. It has therefore been desired to provide synthetic intermediates which permit advantageous preparation of natural camptothecin having the S-configuration and its derivatives.